I have an 2000 Disco, 278K on the odo and running great! But, it has developed a "thrumming" that starts at 46 mph and smooths out at about 52-55 mph. I have a magna flow exhaust on the truck, as well as an Atlantic British long block engine installed just 6K ago, so I know its not an engine noise. I know from reading in this forum that the Magnaflow exhaust does have a "thrum" or drone as well at a certain speed so I don't know if its exhaust related.

If it's wheel related, which is what I concerns me the most, how to tell what side and/or what end? I just had a local transmission shop install a rebuilt rear diff due to movement up and down in the pinion and metal shavings in the oil, so the problem's not there. You can feel the vibration in the floorboard as well. The vibration was present before the rear end work. The rotoflex is new and was installed when the rebuilt rear end was installed. I installed a Tom Woods front driveshaft a while back, and have been most faithful with greasing all the fittings.

Don't want to just throw parts at it, but also don't want to ignore something that could be catastrophic. Could it just be the vibration of the Magnaflow exhaust? I did not notice any vibrations/"thrums" until it was installed.

Thoughts greatly appreciated.

Thanks as always for your input.

 

check front driveshaft carefully again.

 

take the front driveshaft off and lock the CDL. drive it and see if it goes away. do the same with the rear if you have the sound still. That will help you determine if the driveshafts are the culprit or if you need to dig deeper